The URL can be used to link to this page

Home My WebLink AboutMisc-~ Schweikl & Associates, pllc Civil Engineering, Project Management, & Consulting PRELIMINARY '.J_!ECHNICAL INFORMATION . REPORT FOR SE 192ND STREET SHORT PLAT PROJECT NO: 14189 FEBRUARY 2015 PREPARED FOR: MRS. SHERRILL K. HERBEL 23821 124TH AVE SE KENT, WASHINGTON 98031-3609 PREPARED BY: BRANT A. SCHWEIKL, P.E. SCHWEIKL AND ASSOCIATES, PLLC. 1945 SOUTH 375TH STREET FEDERAL WAY, WA 98003 (253) 226-4508 RECEIVED APR 2 3 2015 CITY OF REN'TON PLANNING DIVISION PRELIMINARY TECHNICAL INFORMATION REPORT FOR SE 192°d Street Short Plat llOxxx SE 192°d Street. Renton, Washington 98055 . February 2015 Prepared Ior: MRS. SHERRILL K. HERBEL 23821 124TH AVE SE KENT, WASHINGTON 98031-3609 Prepared by: Brant A. Schweikl, P.E. REPORT #14189 oi·~· I~ "I hereby state that this Storm Drainage Report for SE 192nd Street Short Plat has been prepared by me or under my supervision and meets the standard of care and expertise which is usual and customary in this community of professional engineers. I understand that the City of Renton does not and will not assume liability for the sufficiency, suitability or performance of drainage facilities prepared by me." This analysis is based on data and records either supplied to, or obtained by, Schweikl and Associates, pile. These documents are referenced within the text of the analysis. The analysis has been prepared utilizing procedures and practices within the standard accepted practices of the industry. · • 2 ·~ Schweikl & Associates, pile Civil Engineering, Project Management and Consulting February 10, 2015 Preliminary Short Plat Drainage Report Project: SE 192nd Street -Preliminary Short Plat Table of Contents 1. Technical Information Report (TIR) Worksheet 2. Section 1: Project Overview 3. Section 2: Conditions an Requirements Summary 4. Section 3: Offsite Analysis 1945 S. 375th Street Federal Way, WA 98003 Phone: (253) 226--4508 bschweild@SAcivit.net 5. Section 4: Flow Control & Water Quality Analysis and Design Page3a Page4 Page6 Page7 Page8 Page 11 Page 12 Page 12 Page 12 Page 13 Page 13 6. Section 5: Conveyance System Analysis and Design 7. Section: 6: Special Reports and Studies 8. Section 7: Other Permit 9. Section 8: CSWPP Analysis and Design 10. Section 9: Bond Quantity, Facility Summaries 11. Section 10: Operations and Maintenance Manual 12. Attachments ) ' KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Project Owner SH~~! L.!... }(, ~' ,. ":-: c' '--· Phone~---~----~-~ Address t-:3".'--Z..I I Z4 i ~ A \J-,.;: ~l~- k f".1-1\ / \r/+I , $oz (-,;Cc(? Project Engineer {2f"'.A ,rr A, ;Ser ,1,-: ,>.1 .~ Company L-cl sc,:_., 'PU-u Phone Zb-4-'3C>-~ Part 3 TYPE OF PERMIT APPLICATION JZ!Landuse~ Subdivlson /i~hortSu~/ UPD 0 Building S~ M/F I Commerical I SFR CJ Clearing and Grading CJ Right-of-Way Use CJ Other Parts PLAN AND REPORT INFORMATION Technical Information Report Type of Drainage Review WI Targeted (circle): Large Site Date (include revision dates): Date of Final: Part 6 ADJUSTMENT APPROVALS I Part 2 PROJECT LOCATION AND DESCRIPTION Project Name DOES Permit# location Township :::zz·~) Range t6 E. -:z -,, Section ----'"'-=,,__,'--~ Site Address \ \ D >¢'. SIS ,.c;--z:, rci ':'7,'f'.<::""'" Part 4 OTHER REVIEWS AND PERMITS CJ DFWHPA CJ COE404 CJ DOE Dam Safety 0 FEMA Floodplain 0 COE Wetlands 0 Shoreline Management CJ Structural RockeryNault/ __ 0 ESA Secti0n 7 9( Other 'RovJ 1 t7u•-·~1 >--tG Site Improvement Plan (Engr. Plans) Type (circle one): Full / Modified I Small Site/ Date (include revision u !. dates): r Date of Final: Type (circle one): Standard I Complex I Preapplication I Experimental I Blanket Description: (include conditions in TIR Section 2) p~ Iv,_, N f\-'2'f T :r.:e. ~:>-c : ,. :, R-T 'B ,,7 s':'fz uA,--,u" Date of Aooroval: 2009 Surface Water Design Manual ]/9/2009 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 7 MONITORING REQUIREMENTS . Monitoring Required: Yes~, Describe: Ar I J ' I • Start Date: !L/6. Completion Date: 'N',, ~r I f-c Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan : f'"" Nm ;,J Special District Overlays: _____________________ _ Drainage Basin: D<.J W/..M 1,;.d -· .<'1Tc"• i g·, Vlff,;'...1 bt..-lr'Cv p::, vi'!' rz:. StormwaterRequirements: Lt;;..yfl:L 2-FLouJ C6Jc.JD2o1;:,, 13 ~1c ,..,Jq, Part 9 ONSITE AND ADJACENT SENSITIVE AREAS CJ River/Stream --------- CJ Lake CJ \/Vettands _________ _ Q Closed Depression -------CJ Floodplain _________ _ Q Other __________ _ Part 10 SOI LS 0 Steep Slope -------- 0 Erosion Hazard ------- 0 Landslide Hazard------- 0 Coal Mine Hazard ______ _ Q Seismic Hazard ------- 0 Habitat Protection------- fa" Nol.If- Soil Type /, ~ \ Slopes .,, Erosion Potential 41..-17pe_\t,.IO.'\\:, (A'J0) O-Z,1"3'l fl{ I N 1 IJ., /kL. ht..t--. D---z..--ri.Z ,NI., (I I t, d::I. : High Groundwater Table (w~hin 5 feet) Other R Lk l:J Sole Source Aquifer Q Seeps/Springs Q Additional Sheets Attached 2009 Surface Water Design Manual 1/9/2009 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE CJ Core 2 -Offsite Analysis CJ Sensitive/Critical Areas CJ SEPA LIMITATION/ SITE CONSTRAINT ~ Other HH-:/w~1f(ZTf1t,,L;; I tf f--t_. ~ 0 rre (o&c;qp1.1-J -FC4t..1 v D I CJ Additional Sheets Attached Part 12 TIR SUMMARY SHEET lnrovide one TIR Summarv Sheet ner Threshold Dischame Area) Threshold Dlecharge Area: (name or description) )JI . .-·:r;:.. Core Requirements (all 8 apply) Discharge at Natural Location Number of Natural Discharae Locations: Offsite Analysis Level: ·1./2/3 dated: 7 I ;;, ·; /C I Flow Control L-1 D Level: 1 / 2 I 3 or Exemption Number "'MAJD!i<-.D (incl. facility summary sheet) Small Site BMPs P'EJ2J [(:Jy=,-P'f ,y;,yJ" ,.,. =ii;: Conveyance System Spill containment located at: -.. I /A , Erosion and Sediment Control ESC Site Supervisor: . ,:::'.c;,NT12,,:e:n::, R._ ,-.D I Contact Phone: Y!E.T" t,~12.M I ..i E-0 After Hours Phone: Maintenance and Operation Responsibility: ~rivate D Public If Private, Maintenance Loo Reouired: Yes K1YJL) Financial Guarantees and Provided: <DJs.-{ No Liabililv ,c;_, 'T'(_ ~ k',;,. tJT ,,.,_ ""'"'-171/5 Water Quality Type: ~Sens. Lake / Enhanced Basicm / Bog (include facility summary sheet) or Exemption No. Landscaoo Manaoement Plan: Yes/~ Snar.lal R...,uirements las annllcable\ Area Specific Drainage Type: CDA I SDO / MOP / BP/ LMP / Shared Fae. 'I lllone ) R=uirements Name: Floodplain/Floodway Delineation Type: Major/ Minor/ Exemption /~ 1 OD-year Base Flood Elevation (or range): Datum: Flood Protection Facilities Describe: N/Pr Source Control Describe landuse: f:-B. R!:,-.:3 'DJJ!'_ ND M__,.. (comm./industrial landuse) Describe any structural controls: NoNE 2009 Surrace Water Design Manual 1/9/2009 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Oil Control High-use Site: Yes / No Treatment BMP: )a;JZ.\lrbu 5 Co1'JC6,1z]Ji. Maintenance Agreement: with whom? Other Draina e Structuree Describe: Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION AFTER CONSTRUCTION !Sa: Clearing Limits ~ Stabilize Exposed Surfaces ~ Cover Measures Jlr Remove and Restore Temporary ESC Facilities ~. Perimeter Protection ~ Clean and Remove All Silt and Debris, Ensure J:a.. Traffic Area Stabilization Operation of Pennanent Facilities D Sediment Retention 0 Flag limits of SAO and open space D Surface Water Collection preservation areas D Other D Oewatering Control iiiJ Dust Control D Flow Control Part 14 STORMWATER FACILITY DESCRIPTIONS /Note: Include Facililv Summarv and Sketch I Flow Control Tvoe/Descriotion Water Qual"" Tvne/Oescrintion CJ Detention D Biofiltration 0 Infiltration D Wetpoo1 CJ Regional Facility CJ Media Filtration D Shared Facility CJ Oil Control CJ Flow Control CJ Spill Control BMPs F,:.ii-JLCO'> ~Other 4;,}'-X:\<.Ef1": D Flow Control BMPs /tµ;£N/i>~P .r,a: Other ~R\/lC<.>~ ~\L,5, , <" C ?< f'..~.'T ~-_. ,. 2009 Surface Water Design Manual 1/912009 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS D Drainage Easement 0 Cast in Place Vault 0 Covenant Cl Retaining Wall 0 Native Growth Protection Covenant 0 Rockery > 4' High 0 Tract 0 Structural on Steep Slope _ta Other I N~5'SjJE;C.P.f!-::S j l:J Other ' , <,;t, I t ,._, _ :~ Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Techni~nformation Report. To the best of my knowledge the infonnatimn providlld here is.acdlrate.'' . / ~ ;:/-fl . . .·.' -1· , -· .-.. , ,,, ' _;~ ___ .. ..- i: ----' Si 2009 Surface Water Design Manual 1/9/2009 Section 1: Project Overview Toe following drainage report is provided to the City of Renton as part of the preliminary short plat submittal process for the proposed SE 192"d Street Short Plat. Toe project within the City of Renton city limits at 11 Oxx SE l 92"d Street, just east of I 081h Ave SE. Toe current City of Renton zoning is R-8 Residential and the surrounding properties to the north, east and west which lie within the City of Renton are also in R-8 zoning. To the south of the SE !92"d Street Right-of-Way (ROW) is within the City of Kent and the current zoning is Garden Density Multifamily (MR-0). With respect to storm drainage and water quality design standards and the application of the 2009 King County Surface Water Design Manual (KCSWDM 2009) and City of Renton Amendments to the 2009 KCSWDM the proposed parcel lies in the Duwamish- Green River watershed contained within the Black River drainage basin. The project also lies within the Water Resource Inventory Area 9 (WIRA 9). Toe proposed land use development project intends upon subdividing a single parcel, Parcel No: 6623400131, into two individual parcels through a Short Plat subdivision process. The parcel area prior to dedication is 21,953 sf and will be required to dedicate an addition 5-foot strip of property along the SE 192nd Street ROW to the City of Kent, who administers to the SE 192°d .Street public ROW. Toe area to be dedicated to the City of Kent totals 795 sf and the remaining developable property area is 21,158 sf. Toe City of Renton requires a minimum of IO-foot wide onsite landscaping along the SE 192nd Street ROW, provided. Toe R-8 zoning dimensional and area requirements area as follow: Minimum Lot Area: Minimum Lot Width: Minimum Lot Width (Comer Lots) Minimum Lot Depth: Front Setback: (garage front) Rear Setback: Side Setback: Side Setback (along street) Maximum Height: Maximum Building Lot Coverage Maximum Impervious Coverage 5000 sqft 50 ft 60 ft 80 ft 20 ft 20 ft 5 ft 15 ft 30 ft 35% or 2500 sf for lots over 5000 sqft 75% The project lot layout proposes the following; Number of Lots, Density and Range of Lot Size: Number of Lots: = 2 Density: = 5.24 du/ac Lot Sizes: w/o easement = Maximum: 8,755 sf(Lot I) 4 Minimum: Average: 7,880 sf(Lot 2) 8,318 sf The proposed lot configuration is such that there is a proposed 20-foot wide private driveway access that is proposed run north to south near the western parcel boundary. The proposed private driveway access win lie upon a proposed 34-foot wide ingress/egress and utility easement that will be to the benefit to both Lots 1 & 2 of the project and Parcel 6623400133, which lies to the north of the parcel and is currently accessed via an existing 20-foot wide ingress/egress and utility easement in place. The proposed short plat will create a new 14-foot wide ingress/egress and utilities easement adjacent to the western edge of the existing easement that will create a total easement width of 34 feet. The current access to Parcel 662340013 3 is an existing private gravel access driveway that lies predominately within the existing 20-foot wide ingress/egress and utilities easement. Soil Type and Drainage Conditions: A Geotechnical Engineering Study was performed by Earth Solutions NW, LLC, dated 2/4/14, that describes the existing onsite soils for the purposes developing the property for two single-family residential structures. The subsurface exploration was completed on January 20, 2014 and groundwater seepage was encountered between depths of approximately three and one-half to seven feet below the existing grades. The existing parcel soils include four to six inches of topsoil overtop anywhere from three to five and one-half feet of fill consisting ofloose silty sand with gravel and loose poorly graded gravel with sand. The moisture content of the fill was characterized as moist to wet. Directly below the imported fill material is an Alderwood gravelly sandy loam (AgC), which was classified as moist to wet in all test pits. Iron oxide staining was generally encountered between four and one-half to six and one-half feet below existing grades. The existing drainage pattern for the parcel is generally a gradual sloping sheet flow across the grassed surface from an east north-east direction to the west south-west portion of the parcel. The existing grades onsite vary between 0% and 2.75%. There are no existing storm drainage features located on the site. There an existing public Type 1 Catch Basin located within the SE l 92"d Street ROW at in the curb line near the southwest comer of the parcel. The catch basin's rim elevation is 347.1 and there are 12" dia. CPEP pipe(s), E and SW, at an invert elevation of 344.25. The existing soil conditions, groundwater and available head of the existing public storm drainage system in the SE 192nd Street ROW severely limit storm drainage flow control BMP methodologies. In light of the existing soils being imported fill down to the level of the existing wet AgC soils and the groundwater seepage level the opportunity to infiltrate targeted stormwater runoff for flow control is not possible. Therefore with infiltration eliminated physically as a flow control option we then look to onsite detention and release as a possible flow control BMP. Due to the fact that the existing public storm drainage conveyance system is to shallow to provide for either vault(s)/tank(s) volume storage underneath the private access driveway 5 with proper cover above either system removes these as viable options for stormwater flow control for the project. Therefore without the unreasonable addition of a large quantity of imported fill material placed over the entire parcel site to raise grades and thus grossly altering existing neighborhood surface water flow patterns and reasonable access to the exiting single-family residence on tax lot 662340 0133, the option of underground detention is not feasible. Therefore we are proposing to provide the best available Low Impact Development (LID) concepts to address the stormwater runoff from the project. Our proposal is to install pervious concrete with a shallow storage layer for all new impervious surfaces for the site (driveway access and driveways, amending existing topsoils with organic material to assist in improving runoff absorption, water holding capability and increase shallow infiltration capacity, along with the incorporation of roof downspout splash blocks. Proposed Offsite Improvements: The City of Kent has jurisdictional authority over the SE 192nd Street public ROW and has required the developer to install the following offsite public street improvements. 1. Remove existing easterly most driveway approach and replace with new cement concrete vertical curb, gutter and sidewalk. 2. Modify and replace the necessary portions of the westerly cement concrete driveway approach to accommodate the new alignment and width of the proposed 20-foot wide pervious cement concrete private access driveway. The proposed private infrastructure will also include the installation of one new domestic water service that will require the saw cutting of the existing asphalt and replacement to tap the existing 12" dia domestic water main that lies 13 feet north of the centerline of the public ROW. City of Kent Right-of-Way permit and water service permit from Soos Creek Water and Sewer district will be required. Section 2: Conditions and Requirements Summary The City of Renton Preliminary Short Plat Pre-Application summary report requirements include the City of Renton R-8 zoning requirements as specified above in Section 1 as general zoning requirements. The summary also includes the requirement for two off street par~ stalls parking stalls (in proposed driveway), IO-foot wide landscaping along the SE 192 Street ROW, and a lengthy list of development fees for submittal. The City of Kent has jurisdictional authority over the SE 192nd Street public ROW and has required the developer to install the following offsite public street improvements. I. Remove existing easterly most driveway approach and replace with new cement concrete vertical curb, gutter and sidewalk. 6 2. Modify and replace the necessary portions of the westerly cement concrete driveway approach to accommodate the new alignment and width of the proposed 20-foot wide pervious cement concrete private access driveway. The project will receive its complete plat conditions and requirements once the plat has completed it Preliminary Plat submittal process. The preliminary plat submittal has been created with respect to the City of Renton Municipal Code and the 2009 King County Surface Water Design Manual (KCSWDM). Section 3: Offsite Analysis The Level l downstream analysis was conducted on February 5, 2015, the weather was overcast approximately 51 degrees and scattered showers. Due to recent precipitation event that occurred prior to the downstream field visit there was residual surface water runoff flow within the existing storm drainage features observed in the field. The assumed discharge point with respect to the Level l downstream analysis is to be the existing Type l Catch Basin (CB), PT A, located in the northern curb line of the SE 192nd Street ROW, at the southwest corner of the parcel. The Type 1 CB has 2 -12"0 CPEP inverts, in from the east (-2.85 ft, 0.7%) and out to the southwest (-2.85 ft, 3.3%) to another Type l CB, PT B (o+ 10), solid locking lid, within the current traveled way. The Type 1 CB at PT A was installed as a new alignment CB during a past public road widening project. The public ROW improvements that were the impetuous for the installation for the Type I CB, PT A, was most likely associated with the development of the Plat of Chinquapin Ridge. The existing public vertical cement concrete curb ends at the west side of the existing driveway approach at the southwest corner of the parcel. From PT B, the downstream travels west 170 lfto PT C (1+80), a Type 1 CB in front of House# 11014. The inverts are a 12"0 CPEP from the east (-2.35 ft, 1.0%) and a 12"0 CPEP to the west (-2.55 ft, ±10.4%). From PT C, the public tightlined conveyance system travels ±184 If westward to PT D, (3+64), a Type 1 CB with three pipe inverts. Pipe inverts are a 12"0 CPEP (-3.6 ft) northeast (from Village Gate), and 2 15"0 CPEP inverts, CPEP east (-4.35 ft) and CPEP west (-4.35 ft), water flowing and unable to measure slope due to CB depth. At 4+47 downstream the system enters a Type 1 CB, w/curb thru inlet and vertical curb, PT E, with 2 15"0 CPEP inverts. The inverts are from the east (-5.40 ft) and west (-5.45 ft) with flowing runoff, clean. Sta 5+o0 the system enters a Type 2 CB, PT F, locking lid (unable to open). Identified that there is a 8"0 PVC stub entering PT F from the north and it is an outlet from an existing storm drainage detention pond and downstream biofiltration swale associated with the Village Gate development. It is assumed that the other two inverts are 2 -15"0 CPEP pipes, east and west Sta 5+14, Type 2 CB, PT G, Jocked lid, assumed inverts 2 -15"0 CPEP pipes, form the east and then directs the flow to the south across the SE 192°d Street ROW and to a discharge what would appear to be located south behind the single family developments that are adjacent to the southern edge of the SE 192•d Street ROW. We were unable to access the presumed location due to private property access. The other possible option would be that the downstream proceeds westward in a tightlined public conveyance system to a discharge 7 point to the west of 1081h Ave SE where it would discharge into Panther Creek as it crosses SE 192nd Street from south to north. This possible route seems improbable due to scope of the potential conveyance system and the natural low topographic areas to the south PT G and SE l 92"d Street would have been the natural flow path prior to residential and public ROW development. From PT G we checked a Type 1 CB, locking vaned grate, in the vertical curb line that was just west of PT G The Type 1 CB has 2 12"0 CPEP inverts, west (-3.3 ft) and north ( -3.3 ft). This CB exhibited much less flow than our observed downstream path and it was evident that it was not connected to PT (l Without further access permission from several private property owners it is assumed that the downstream path is conveyed via a minimum 15"0 public conveyance system to an existing natural low lying depression on Tax Parcel: 6623400150, Sta ±10+95 (undeveloped) where it most likely is discharge to the a native broad stream course that is conveyed in varying widths it the existing SE 196th Street public ROW, at Sta ±19+80. From this point there is a 24"0 CMP culvert with a beveled trash rack located within the road side public northern ditch near the common of Parcels 6623401253 and 6623401260. This culvert would appear to convey stormwater runoff from the public ditch system the west where to where it is discharge into Panther Creek as it crosses the SE 1961h Street ROW just east of 108th Ave SE. As a summary of the observed downstream elements that make up the Level 1 Downstream Analysis for the project we did not observe any apparent system restrictions, Jamage, sediment laden or eroded natural conveyance channels that would prevent the SE 192nd Street Short Plat from releasing onsite storm drainage runoff to the downstream public conveyance system. Section 4: Flow Control & Water Quality Analysis and Design The project site was analyzed with respect to the 2009 KCSWDM storm drainage flow control and water quality design criteria. As reviewing the manual it was apparent that the existing site soils, ground water level and exiting topographic elevation with respect to the existing public storm drainage conveyance system with the SE 192nd Street ROW radically eliminated the available flow control options for the development of the parcel. The following is the review of the 2009 KCSWDM available flow control and associated water quality methodologies with their prospects for application for the project. Soils A Geotechnical Engineering Study was performed by Earth Solutions·NW, l..LC, dated 2/4/14, that describes the existing onsite soils for the purposes developing the property for . two single-family residential structures. The subsurface exploration was completed on January 20, 2014 and groundwater seepage was encountered between depths of approximately three and one-half to seven feet below the existing grades. The existing parcel soils include four to six inches of topsoil overtop anywhere from 3 to 5.5 feet of fill consisting ofloose silty sand with gravel and loose poorly graded gravel with sand. The 8 moisture content of the fill was characterized as moist to wet. Directly below the imported fill material is an Alderwood gravelly sandy loam (AgC), which was classified as moist to wet in all test pits. Iron oxide staining was generally encountered between four and one-half to six and one-half feet below existing grades. Onsite Infiltration Per the 2009 KCSWDM, Sections 5.4.2.1, 5.4.3.1, 5.4.4.1 & 5.4.5.1, inf"lltration of stormwater shall be infiltrated with the bottom of any proposed inf"lltration facility (trench/pond) shall be one-foot into "native soils" and the bottom of the facility shall be three feet above the above the seasonal groundwater level or a permeable soil layer. Our parcel has past fill material in place that bas a seasonal groundwater level within approximately one plus feet from the bottom of said fills. Therefore per the limiting existing site soil conditions and the KCSWDM there are no traditional infiltration design methodologies available for application on our project site to address onsite flow control and/or water quality treatment. Once we have investigated the project site for the possibility of infiltration as a possible flow control BMP, the next step in selecting a flow control methodology is to analyze the project site for a detention and release flow control facility. Onsite Detention The existing onsite drainage for the parcel is generally a.gradual sloping sheet t1ow acrQSS the grassed surface from an east northeast direction to the west southwest portion of the parcel. The existing gradual grades onsite vary between O"/o and 2. 75%. There are no existing storm drainage features located on the site, but there is an existing City of Renton public biofiltration swale downstream of the detention pond for Plat of Chinquapin Ridge adjacent to the eastern property line of the parcel. There is an existing public Type 1 Catch Basin located within the SE 192nd Street ROW at in the curb line near the southwest comer of the parcel. The catch basin's rim elevation is 471.4 (survey) and there are 12"0. CPEP pipe(s), E and SW, at an invert elevation of 468.55 (field measure down). Analysis of the existing topographical grades of the site and the existing discharge invert elevation (468.55) indicate that there is insufficient grade difference (depth of public conveyance system) between the grades of the proposed site and the public conveyance system invert to provide an underground detention facility with proper cover (minimum 2' of cover) within the private ingress/egress and utility easement. Such a facility would . likely be located at the lowest point of the parcel, therefore the southwest comer of the · parcel directly north of the SE 192"d Street ROW. With the small onsite surface water flows generated it would be most likely that the existing flows with the public conveyance system will backflow into any onsite underground detention facility and eliminate any onsite storage volume provided. Any import of fill material to raise the site enough to (approx 2') would adversely affect 9 the natural drainage patterns for Parcel 6623400133 to the north of the project. The fill would leave parcel 6623400133 well below the fill on our project and potentially trap on and offsite stormwater that sheet flows onto the parcel from the north, causing new onsite ponding, long duration saturation of the existing yard and potential groundwater infiltration/flooding into the existing residential structures crawl space. There are other unintended consequences associated with the importation of a fill on our project site that would be created. The unintended consequences are that with additional 1500 cubic yards of fill material that would be required the fill will have to be trucked onto the site via the public roadway system and there shall be an increased probability of the spread of dust and material over the route truck path and increased wear on the public pavement structures. Therefore due to the fact that the existing public storm drainage conveyance system is to shallow to provide either vault(s)/tank(s) volume storage underneath the private access driveway with proper cover above either system it is neither practically feasible nor desirable. Without the unreasonable addition of a large quantity of imported fill material placed over the entire parcel site to raise grades and thus grossly altering existing neighborhood surface water flow patterns and reasonable access to the exiting single- family residence on tax lot 662340 0133, the option of underground detention is not feasible. Proposed Low Impact Development (LID) Therefore we are proposing to provide the best available Low Impact Development (LID) concepts to address the stormwater runoff from the project. Our proposal is to install pervious cement concrete with a shallow rock storage layer for all new impervious surfaces for the site (driveway access and individual driveways) and amending existing topsoils with organic material. By salvaging the existing topsoil onsite and amending the final 8" depth of soils with organic compost. Amending the soils would vastly increase onsite stormwater runoff absorption, water holding capability and increase shallow infiltration capacity. According to Low Impact Development -Technical Guidance Manual for Puget Sound, Section 6.2, Amending Construction Site Soils, indicates that a University of Washington study determined that the application of amended soils to pervious areas can reduce the amount of surface runoff from the area of amended pervious soils by between 53% to 70%. This LID option would include the incorporation of roof downspout splash blocks to disperse the roof downspout flows energy and direct surface sheet flow to the eastern portion of the parcel where the greatest possible flow path and the largest area of amended soils are available. The application of amended soils on the project would be in compliance with tlie Low Impact Development-Technical Guidance Manual for Puget Sound, Section 6.2.2. In summary all pervious soils would be amended such that the turf areas would have an organic compost content of 5% to a settled depth of 8" and a 10% organic content for the landscaped area to a sett! ed depth of 8". The proposal to utilize impervious cement concrete pavement for the traditional 10 .. impervious surfaces associated with the private driveway access driveway and the individual lot driveways is intended to address both flow control and water quality treatment in place of traditional flow control methodologies not available for this project The proposed 3,989 sf of 5" thick pervious concrete pavement for the project will placed over a 6" deep gravel storage bed to store and retain stormwater reaching the pavement surface. The stormwater collected within the pervious concrete pavement section and the gravel storage bed will be infiltrated into the existing soils underneath the driveway at the rate of the existing onsite fill materials. The ~e of the proposed driveway pavement would be 1.45% to the south and the SE 192" Street public ROW. All proposed landscape areas adjacent to the pervious cement concrete pavement we are proposing 18" wide 6" deep washed rock aprons to provide protection from surface water flowing direct to the pervious pavement surface. Water Quality Treatment Our LID proposal would also address water quality treatment for the Pollution Generating Impervious Surfaces (PGIS) or those surfaces subject to vehicular traffic, the private driveway access and individual driveways. According to the Low Impact Development - Technical Guidance Manual for Puget Sound, Section 6.3.5, Water Quality, the pervious concrete pavement with a gravel storage layer removes 'substantial portion of heavy metals and automobile mineral oils. The research and laboratory studies referenced within the Guidance Manual indicate that the removal capacity "of89 to 98 percent for·lead, 74 to 98 percent for cadmium, 89 to 96 percent for copper, and 72 t0 98 percent for zinc". The same study excavated a 15-year old pervious surface and found no significant concentrations of heavy metals. Another study showed a 97.6 percent removal of automobile mineral oil in a pervious pavement section. The removal of automobile mineral oils is attributable largely to natural biological breakdown by microbial activity within the porosity of the pervious concrete pavement and the gravel storage layer. This is a removal level that exceeds the levels that could be attained by a detention tank or vault including a static water quality treatment volume due to the specific gravity of oils and the difficulty of removal of said oils in a settlement Water Quality storage based BMP. The stormwater runoff generated by the new single-family residential structure is deemed clean un-polluted runoff and therefore would not require water treatment But with our proposal to sheet flow the roof runoff across the organically amended soils of the proposed lawn area that we would be obtaining.an increased level of pollutant/heavy metal removal than the a traditional sedimentary water quality treatment volume. " Section 5: Conveyance System Analysis and Design The LID proposal does not include the installation of an onsite private conveyance system or any additions or revisions to the public offsite conveyance system. The existing natural point of discharge is sheet flow to the south-southwest direction and eventually reaching II the SE 192nd Street ROW. Our proposed LID design would direct the roof area and areas of the lot 20-feet east of the private driveway ingress/egress and utilities easement (all area except the front yards) will be direct to the east. The flows will enter the existing City of Renton biofiltration swale adjacent to the eastern property line. There is sufficient volume and flow capacity within the design of the existing biofiltration facility to accommodate the small amount of runoff that might reach the swale after the proposed soil absorption of the organically amended turf and landscape soils. The front yards would be confined behind the bermed landscaping beds that are adjacent to the private driveway access. The LID design intends to infiltrate the precipitation that falls upon the pervious concrete pavement inplace within the pervious cement concrete pavement layer and the gravel storage layer below. If the maximum precipitation storage were to be reached the runoff would sheet flow from the pervious pavement surface in the same manner of the existing site with no design point discharges. Section 6: Special Reports and Studies A Geotechnical Engineering Study was performed by Earth Solutions NW, LLC, dated 2/4/14 (See Attachments) No SEPA is required and there are no other special studies that were prepared within respect to this submittal and there are no other special studies that we are aware of that pertain to the development of the parcel. Section 7: Other. Permits Other than the Preliminary Short Plat approval that we are applying for with this submittal the project will require Final Engineering Design Documents (City of Renton), Right-of Way permit (City of Kent) and utility connection permits for one (1) new water service and two (2) new residential water meters (Soos Creek) and two (2) side sewer connection permits to the two existing 6"0 sanitary sewer services that extend to the northern edge of the SE 192nd Street ROW line (Soos Creek). Section 8: CSWPPP Analysis and Design The Construction Stormwater Pollution Prevention Plan (CSWPPP) for the project includes the use of a temporary construction entrance, catch basin protection for the existing public catch basins within the SE 192nd Street ROW within 200-feet downstream of the SE comer of the parcel, sediment stockpile protection and sedimentation fence completely surrounding the parcel. The CSWPPP shall include salvage of the existing onsite topsoils to the extent possible for reuse on site. The stockpiles shall be located along the northern property line and protected with plastic cover. The private driveway access pervious concrete pavement shall not be install until the project has been final graded and the site grassed lawn areas and landscaped areas have been installed and stabilized. No soils or landscaping material shall be temporary placed upon the installed pervious pavement section at anytime. The CSWPPP/femporary Erosion Control Plan to be created as part of the final engineering 12 documents shall be designed per and contemn to the 2009 KCSWDM and the City of Renton Amendments to the 2009 KCSWDM. Section 9: Bond Quantities, Facility Summaries, and Declaration of Covenant There are no traditional storm drainage infiltration or detention facilities proposed with our LID project design and therefore the Facilities Summaries do not apply. A Bond Quantity Worksheet will be prepared and submitted with the Final Engineering Documents submittal once the final project infrastructure is conditionally approved with approval of the preliminary Short Plat by the City of Renton. Section 10: Operatiom and Maintenance Manual Other than the pervious concrete pavement there are no traditional storm drainage detention/retention, conveyance system or other permanent storm drainage features that require maintenance per Appendix A of the 2009 KCSWDM. By our proposal incorporating LID design the knowledge level and maintenance requirements for the storm drainage to be undertaken by the residents is reduced to the maintenance of the pervious concrete pavement section. PERVIOUS CONCRETE SURF ACE MAINTENANCE DOCUMENT Purpose of Document .. ~f~ pul'pos~ vi Lhis '-1w.:u111cnL is tu ..:~t..ilJii:-ii1 d_lt! 111111unu111 prutectivt: 1nca!;urcs ano maintenance requirements for the ··private"' Pervious Concrete pavement that is installed as the project s "private" road pavement. The responsibility for the maintenance and · protection of the pervious concrete pavement surface is the. responsibility of all property owners who have legal easement access to the private ingress/egress and utilities easement. The two proposed lots of the SE 192nd Street Short shall have an equal 1/2 share of the cost of maintenance and repair of the pervious pavement associated with the portion of the pervious pavement within the private ingress/egress and utilities easement along the eastern property line of the SE 192"" Street Short Plat. The individual pervious concrete driveways on the individual lots of the proposed short plat shall be the responsibility of the individual lot owner's. Reason for Pervious Concrete Pavement Pervious concrete pavement, for example. is a permeable pavement surface-typically with an underlying stone reservoir-that temporarily stores/treats surface runoff before it infiltrates into the subsoil.. As such. a pervious concrete pavement is an intricate part of an engineered infiltration system for storm water management. The solution requires specific maintenance to maintain its efficacy. In addition to owners not being aware ofpervious pavement on a site, not performing these maintenance activities is the chiefreason for failure of the pervious pavement/storm water system. 13 Cleaning The majority of pervious concrete pavements will function well with little or no maintenance. There may be instances. however, in which sand, dirt, leaves and other Jebris infiltrate the void structure of the pervious concrete and inhibit its permeability. In most cases, the clogging is limited to the tirst I in. to 1.5 in. of the pavement thickness. Routine cleaning can help avoid this situation and restore the pervious concrete's permeability . . \ study by the University of Central Florida (UCF) looked at three standard maintenance practices for cleaning pervious concrete. The cleaning techniques investigated were pressure washing, vacuum sweeping and a combination of these two methods. Pressure washing dislodges the clogging particles, washing a portion off site and flushing the remaining portion through the pavement surface. Vacuum sweeping with a regenerative vacuum sweeper dislodges dirt and debris by means of the sweeping action and removes them via the vacuum. Results of the UCF study show that utilizing these cleaning practices individually or in combination can improve the infiltration rate of a clogged pervious concrete pavement by 90% or more. Periodic cleaning and checking of the pavement's porosity and rate of water percolation will help maintain the pavement/storm water system to ensure that it will remain functional as designed. Table I can serve as a minimal recommendation for scheduled maintenance . ....,...;c u.l~ ..1u.ac..,ucJ Su11 i.Ji,:gu t .. .'uu,ur r :11.:tiitie!}' -.1.)orow· r'aveme,u Uperauon unti Jfaintenance Protocol. for,the proper specific models of equipment for cleaning, · ;weeping and v:i.cuuming of porous cement concrete pavement. Table 1. I Activity .. A void sealing or repaving Inspect .pervious pavement are to ensure that it: • Is cleaii'of debris; • Dewaters between storms; • Is clean of sediments. Mow upland and adjacent areas and remove vegetation and debris, and seed bare areas. Vacuum sweep surface to remove debris and Sediment. Inspect the surface for deterioration or spalling. 14 Schedule Always Monthly Annually Annually and as necessary Annually Cold-Weather Considerations Experience has shown that pervious concrete pavements in cold-weather climates tend to have an inherent ability to withstand freeze-thaw cycles. Freeze-thaw resistance of pervious concrete appears to depend on the saturation level of the voids in the concrete at the time of freezing. Field observations have shown that the rapid draining characteristics -if pervious concrete prevent saturation from occurring. ft is important to understand that the porosity ot'pervious concrete from the large voids is Jistinctly different from the microscopic air voids that provide protection to the paste in conventional concrete in a freeze-thaw environment. When the large voids are saturated, complete freezing can cause severe damage to the pervious concrete pavement. Thus, it is critical to protect and maintain the void structure of pervious concrete in order to ensure cold-weather durability . . \necdotal evidence also suggests that snow-covered pervious concrete clears more quickly, possibly because its voids allow the snow to melt more quickly than it would on conventional pavements. Mechanical removal of ice and snow can be accomplished using snowblowers or snowplows. Because of its rigid nature, pervious concrete pavement is less susceptible than other flexible paving materials to damage from snowplowing. The void structure of pervious concrete pavement may facilitate" a faster thawing of ice and snow on the pavement surface compared with impervious pavements at temperatures . ,.iouestly l>dow m,ezmg. Surrounding Areas Drainage of all unpaved areas should be directed away from the pervious concrete pavement. ·ff areas a,re allowed to drain onto the pavement, suspended materials may wash into the concrete's voids and eventually reduce its porosity and compromise its service life. At the outset, proper design and construction, including installation of curbs where appropriate, can ensure a controlled flow path of storm water during a storm event and minimize the flow of debris onto the surface of the pervious concrete pavement . ...... PRIVATE LANDSCAPING AT THE BACK OF THE SIDEWALK SHALL BE PLACED AS NOT TO DRAIN ONTO THE SIDEWALK. IF THIS IS NOT POSSIBLE A 18" WIDE CUTOFF TRENCH 6 INCHES DEEP SHALL BE PLACED BETWEEN THE SOURCE OF PRIVATE DRAINAGE AND THE BACK OJ<' THE SIDEWALK TO REMOVE :VIA TERIALS THAT MAY CLOG THE PERVIOUS PAVEMENT. Materials that may impact the porosity of pcrvious concrete pavement, such as sand, leaves and mud, may be conveyed by wind. m,tomobile traffic or other means. 15 Periodic cleaning of the pavement wi 11 minimize the effect of this debris and help maintain the necessary permeability adequate for the pavement/storm water management ;ystem' s designed function. ADDITIONALLY, LANDSCAPING MATERIALS SUCH AS MULCH AND TOPSOIL SHOULD NOT BE STORED DIERCTLY ON THE PAVEMENT, EVEN TEMPORARILY. IF LANDSCAPE MATERIALS OR EXCAVATED SOILS ARE TEMPORARILY STORED ON PRIVATE PROPERTY THE MATERIALS SHALL BE COVERED WITH PLASTIC WHEN WORKING WITH THE MATERIAL AND THE INDIVIDUAL PROPERTY OWNER PROPERTY SHALL BE RESPONSIBLE PREVENTING THE MATERIAL FROM REACHING THE PERVIOUS CONCRETEPAVEMENTWITHSANDBAGSOREQUALPROTECTIVE MEASURES. Summary In summary, the project proposes to install LID Pervious Cement Concrete Pavement and Amended Soils BMP's to address the storm drainage runoff generated by the short plat development, in lieu of the traditional methO!ls of infiltration and detention. The traditional flow control methods are not options due to the existing soil conditions and topographical conditions of the parcel. All design work was prepared in accordance with the 2009 KCSWDM, the-accepted City of Renton drainage design manual and the Low Impact Development -Technical Guidance Manual for Puget Sound. If you should have any questions or require additional information please do not hesitate to contact me, Brant A. Schweikl, at (253) 253-4508, and I will do my best to assist you in any way possible. 16 Geotechnical Engineering·::,. Geology ,f Environmental Scientists• . ~ Construction Monitoring· •:. ' :, . . · ;:.. GEOTECHNICAL ENGINEERING STUDY .~-,,. .. ·:,:· PROPOSED TITUS/ HERBAL ,~t': RESIDENTIAL HOMES '" 110XX SOUTHEAST 192ND STREET ·"'"' . .. :~~ RENTON, WASHINGTON ES-3215 PREPARED FOR PUGET SOUND HOMES, LLC January 28, 2014 Revised February 4, 2014 ~.41'~ Keven D. Hoffmann, E.I.T. Staff Engineer Kyle R. Campbell, P.E. Principal GEOTECHNICAL ENGINEERING STUDY PROPOSED TITUS/HERBAL RESIDENTIAL HOMES 110XX SOUTHEAST 192ND STREET RENTON, WASHINGTON ES-3216 Earth Solutions NW, LLC 1805-136111 Place Northeast, Suite 201 aenevue, Washington 98005 Phone: 425-449-4704 Fax: 425-449-4711 Toll Free: 866-336-8710 Important Information About Your Geotechnical Engineering Report . . ' ' --' ' ' I' ' ' ' / ' ~ ' \ I • I '-I GlulWI 1~11 IIPVlal 11'1 Pa•J1111 r. 8'li:.tlc Pa ;1111, Pa m-. al Pr1J1c11 Geoteclmlcal engineers stnx:ture lhelr services Ill meet lhe spoofic needs of their cJlenls. A geolechnical engineering study coorucl9:l lor a civil engi- neer may not fulfill the needs of a conslnJ:tion contraclDI or ewn another civil engineer. B8C3lS8 each geolechnkal engineering study is unique, each geoteclrliral engineering report is unique, prepired solll/yu Ille client No ore e,a;eit you should rely on )'Oll' geotechnical engineefing report without first con1811ing with the gecachnlcal engineer who prepared It. And no one -/IOtl!l'/J(1.lflU-should applylhe report for ll1Y purpose or projoct mept lhe one origlrally cootemplaled. Rimi 1111 FIi RIP l Serious problems haw occurred because lhose relying on a geoteclmical engineering report did not mad It. all. Do not rely on an executive summary. Do not read seleclilll efemenls only. A GI atwl I II Engineering Rl°rt II 1111811 111 A It 71 Ill II Pl'IIJact-Specil FICIDI I Geotechnical engineers consider a nunber of unique, project-specific lac- , tors when establlslllng Ille scope of a Sl!Jdy. Typical fadors include: Ille client's goals, objedlves, and risk managemert prefelences; Ille general nature of the strudure inwlved, 11s size, and configuration; Ille location of the structure on Ille site; and olller planned or IIXisllng sil8 improvements, such as access roads, parlclng lolS, and underground wlilres. Unless the geol8clmlcal engineer who cond!J:led Ille Sllldy speclflcally Indicates oth- erwise, do not rely on a geo1Echnical engi.-lng report that was: • not pmpared for you, • not prepared for your project, • not prepared for the specific site explOllld, or • completed before impooant project Changes were made. Typical changes that can erode the reliability of an existing geotechnical engineering report include those that affect: • the function of Ille proposed structure, as when ifs cllanged from a par1cing garage to an office building, or from a light industrial plant to a refrigerated warehouse, • elewtion. configuration, localon, orientalion, or weight of Ille proposed stru:ture, • composition of the design team, or • project ownership. As a general rule, alway.s inform your geotschnlcal engineer of project ~ minor Clll8il-illCI J8(JJ8SI an assessue,t ol their irJ'8i Geolechnir,aJ £ll1(Jinrets carm ;m//Jt responsibility or liability tor pmbJems fh;t occur becavss their lff/OIIS do not W1Skkr d/N8lopmenfs a w/lial //ley llfllll not infoml/11. 1ft rra:,cm•waacan t• A geotechnlcal engineering report is based on conditions that existad at the time the studlj was performed. Do not re/'/ on a geotec/Jnlca/ er,gineer- ing mportwllose adeQull;'/ may have been affected by; Ille passage of time; by man--madil events, such as consbuction on or adjilCIIIII to the slla; or by natural ewnlS, such as floods, earthquakes, or groundwater fluctua- tions. Always contlx Ille gaotechnlcal engineer before ~lying Ille report to determine n tt Is still reliable. A minor amooot of additional ll!sting or analysis could prevent major problems. MIit G1111tl 5 II~ 11'1 Pr•11l1LP.11 ... Sile exploration identlffes subsurface condllfons only at those points wl1ere substnfare teslS are conduded or samples aretalell. Geotecl1nical engi- neers review field and laboratory data and then apply their pmresslonal judgment ID render an opinion about subsurface conditions lllroughoii the site. At1UaJ subsurfze conditions may difler-5D1111!11mes significantly-- from those indicaled in your report Retaining Ille geotechnlcal engineer who developed your report ID provide construdion observation is the most ell8cllve melhod of managing the risks associated willl unanticipated conditions. AR ••• r, Rau lllllia 11'1-FIIII Do not overrely on lhe construcllon recomfl180dations included in your report Those f8COfmlel1dallo ill1I not final, because geoteclmical ~f- neen; develop them principally from judgment and opinion. Geotechnical engineers can finalize llleir recomrnendatJon only by observing actual --···-----. ------------·---·-_) ( subsurta:e coodilin revealed during construttlon. 1he geolBChnical tlfYJ/t1(Je( who developed yw tepOfi C8flllOI /lSSll1lfl rr,sponsibi/ity Of liabilily faf 1111 lllf)Oll's tBaX11l118l1dal if that engineer does nd perform constnJdJon liXieMt/on. A GIIIICDal;JI Dllllrna lnl-1 'I II IMlllttl ID llllllilli ........ Olher design fElm rranbers' mislnleipietatilln of gealedmical engi'leer!IQ reports has restdled in~ ll«)blerm. Lawer that risk by tiaving yo .. geo- ledlnica! engineer COllfer wlVl illJproprialB l11lll1bers of the design learn after milling the report Also l1'llain your geofect,oical engineer to review pelli- rllrt elements Ii the desi!JI Bill's pla1s alld specllicatlans. Comms (31 also mislnlelpret a geobichnical engineering report. Rewce lhal ri3k by hlrlfng )'OU! geoleclulical er,Jineer part!cipalB in prebid and preconsln.di/Jn cooerences, aoo by providing conslnM:lion obseMllon. DI Nat RIIII IW Ila fl IP 11 "I LIii Geotechnlcal engineera prep;re final boring and lll5llng logs based upon their inll!i p,etalion of field logs and lalJaratDly dala. To prevent emxs or omissioos, the logs included in a geoleChnical englneaifQ report shoUld ,_ be redrawn foi lnclu.,ton in architedural or other design drawingS. Only photographic or electronic reproduction Is acceplable, lxA recognize that S8/)/Jlllling logs tram 11111 report can tJlevalB risk. r., c.:bWII& 11 C JI 11111£ I• SOme OWl18IS and design professionals mistakenly belleve they can make contraaors liable for unantlcipabid subsurlil:e conditions tr, limltinQ wta !hey provide for bid preparation To he1p prevent cosily problems, give con- lramJS !he oomplete geolBl:hnical engineering raport. bltprefa:e it wilh a Clearly written lellBr of transmitlal. In Ila letter, advise COnllaCIIXS !hat lhe report was not prepared IDr pu,poses of bid developmmt and Iha! lhe report's aa:ancy is limited; encourage hm to confer wittl 1h11 !Jl(lleclmical Bl',llneer WhO prapnd the report (a modest lee may be requiral) and/Or to coodud illkllllonal study ID oblaln the spedflc fypes of information they need or prelet A prebid COl1lelenc:e can also be valuable. BIi sun, CIXllnlJ- tots have sutfkild lilll1 to l*fOnn additional study. Only tllen might you be in a position ID give contradolS !he best lnfoanallon available ID you. while mquirllQ ll1em ID at least SIJare some of the flllallcial responsibilities stemming from unanticipabid condillol1s. 111111 RE&Sllli 11111J 1'1"111111111 CIEIIIJ Some dienls, design professionals, and conlnl:IDrS do not recognilB lhal geotechnical engineering is far less eJCaCt tha1 olf1er engineering disci- plines. This lack of undeffllanding has Cffllled unrealislk: expectations that -------------------.... -...., ha'le led to disappoin1menls, claims, inl disputes. To help rewce the risk of such ouloome.'I, geobichnical engineers commonly Include a variety of explanatory provisions in their reports. SM1elimes labeled 11mitllionS' many of lllese provisions indicalB where geola:llnlcal englneeis' responsf- billties begin and end, to help othelS ll!CO!lflilll 1heir own responsibilities aoo risks. Read these provisions cJosel>( Ask queslions. Your geotecllnlcal engineer should respond fully and !rankly. GHIIIW l&NIIII CIM11 • Ari Nat Gov& UII The equipment, techniques, and personnel used II> pertorm a geoerNiron- menta/ study differ significriy from those used to pertorm a geo/JlChn/caJ sllldy. For 1hal reason. a geolilchnical engineering report does not usually rela!e any !Jl(JenYironmental findings, conclusions, or recommendalions; e.g., about 1111 likelihood of en:ounferfng lflQ!rOIUUlld storage tanks or regulated contamil'lilllls. ~ f1IIYlronmenlll problflms havlJ led Ill numerous project fai/utes. II you have ntt yet obtained your own geoen- vironmental Information, ask your geotedmical consuflant IDr risk nm- agement guldanc:e. Do nd rely on an en'lironmenlaJ f6f)Ofl prepamd tor someone else. •• PN1111l11II IIIIJIMI • 11111 _. MIid DNelSII SlralegieS can be ~ied dlling buiklrQ design, consbU:llon, operalion, and maintenance to prevent signifiaM1I illlOUfflll of mold from growing on Indoor surfaces. To be elllicmv, all such strategies should be de'lised for 111! 8/fl){IJSS purposs"ol mold Jl(Mltlon, integraled Into a corn- prellensiw plan, and 8*lliBd willt diligent CMIISighl bY a proleSllional mold prevention consuffant Because just a small amoort of water or moislUl8 can lead to the deVeJOJIJ]elll of SIM!l8 mold infestations, a num- ber of mold prewntton stra!Egles lows on ksepifQ building surfaces <fly. While groundwaler, wale/ infiltralion, and similar issues may have been _addressed as part of lhe geobichnical engineering slUdy whose findings are conveyed in-this llllJOII. !he geolechnical engineer in chllll8 of this project Is not a mold praventlon COIISUllalll; aone al Ille ™""' ,-. farmtltl ill conndiolr wit/I ,,,. 1HIHllltlal .,,,,,_,,. Sb/If WMI dulgat4 or rondlldld ro, II»,,,,,,,,,. al mold,,,.,.,,. litm. Pmpe, ,,,,,,_,.,,,,,, IIIU,, ____,,_ _,.,, · in 11,ts n,p,,,t rtlll nol tll 11#11 N ""1klttat la ,,,.rtlllt IRtlltl fnJm grow/lJf Ill or aa IN sllw:fae //mJIWd. · 11111 • Ya 16 U II IP Gllk 2 •"Ill flllial' 1• 1171 d Alillla&i Men'ilelSllip in ASff/The Best People on Eanlt expooes geolechnical engl11881S to a wide array ol risk management techniques that can be of genuine belletlt for eve,yone inwlVed wi1l1 a conslruction project. Conllr wi1h you ASFE-member geotecmical engineer for more Information. --------·~·--------------~) A'7FE TU IHI PHIi• H llrll 8811 Colesville ROIIO/Sulbl 6108, Silwr Spring, MD 20910 Telephone: 301/565-2733 Facsimile: 301~2017 &-mall: lnfo@asle.org www.asle.Oll] Capyrfg/11 ltXH 0, ASFE, lllc. ~,.,...._,,or~ olfllls-111-ar 111,,.,._ O,,ny....., -. II st,iclly ,,,-_ -rill A!'::_ ·-----.,,..,..,, .. .---/mffl//J/s_/r __ wfl/llf1' ___ o/JISFE.,nt/gLL- _,,,//t;/Jl//l/flt_O( __ On1v-.o1ASFE-US11t1111-as,_tu aras,n-ota_llcll_ '""""-NW«'- /lrm. lndMdu,/. 0t o,,_.IIIIIIYI/Jat sa .-fllls dacalrrtnt--111 ASFE-cau/tl Ila camm/111nf-or_,_,~- • January 28, 2014 Revised February 4, 2014 ES-3:21.., Puget Sound Homes, LLC P.O. Box 1945 Sumner, Washington 98390 Attention: Mr. Robert Elliott Dear Mr. Elliott: Earth Solutions NW LLC Earth Solutions NW, LLC (ESNW) is pleased to present this report titled "Geotechnical Engineering Study, Proposed Titus/Herbal Residential Homes, 11 OXX -Southeast 192nd Street. Renton, Washington". In our opinion, construction of proposed residential homes is feasible from a geotechnical standpoint. Our study indicates the site 1s primarily underlain by fill and native subglacial till deposits. During our subsurface exploration completed on January 20, 2014, groundwater seepage was encountered between depths of approximately three-and-one- half to seven feet below existing grades. · In our opinion, proposed residential structures can be constructed on competent native soil, recompacted native soil, or new structural fill. In general, competent native deposits were encountered beneath topsoil and fill at depths of approximately three to six feet below existing grades. Where encountered, fill can likely be reworked to the specifications of structural fill, provided it is at or near optimum moisture content at the time of placement and compaction and primarily free of organic and deleterious material. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with a suitable structural fill material, will be necessary. Recommendations for foundation design, site preparation, drainage, preliminary infiltration design, and other pertinent development aspects are provided in this study. We appreciate the opportunity to be of service to you on this project. If you have questions regarding the content of this geotechnical engineering study, please call. Sincerely, EARTH SOLUTIONS NW, LLC ~~~- Keven D. Hoffmann, E.l.T. Staff Engineer , _-I INTRODUCTION ................. . General ........ . Project Description .. . Table of Contents ES-3215 SITE CONDITIONS ................................................................. . Surface ................................................................. . Subsurface •.................................................................. Topsoil and FIii... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........... . Native Soll . . . . . . . . . . . . . . . . ......................................... . Geologic Setting ................................................. . Groundwater........ . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......................... . DISCUSSION AND RECOMMENDATIONS ..................... . General ................................... . Site Preparation and Earthwork .... . Temporary Erosion Control.. . . . . . . . .. . Stripping......................................... . . . .. . . ................. . In-situ Soils. .................................................................. . Imported Soils .............................................................. . Subgrade Preparation.. . ..................................... . Structural Fill ............................................................. . Foundations ........................................................... . Seismic Desian ........................................................... . Slab-On-Gracie Floore ................................................... . Retalnin$1 Wal!!! ................. _ .................................. . Drainage ................................................................................... . Limited Infiltration Design .................................... . Excavations and Slopes.................... . ........................... . Pavement Sections ......................................... . Utility Support and Trench Backfill ............................... . LIMITATIONS ................................... . Additional Services .............. . Earth SalutiOns tN:. ~ - PAGE 1 1 2 2 2 2 3 3 3 3 4 4 4 4 5 5 5 5 fl 6 6 ? 7 8 8 9 9 10 10 10 GRAPHICS Plate 1 Plate 2 Plate 3 Plate 4 APPENDICES Appendix A · Appendix B Table of Contents Cont'd ES-3215 Vicinity Map Test Pit Location Plan Retaining Wall Drainage Detail Footing Drain Detail Subsurface Exploration Test Pit Logs Laboratory Test Results Earth Solutions NW, LlC GEOTECHNICAL ENGINEERING STUDY PROPOSED TITUS/HERBAL RESIDENTIAL HOMES 110XX SOUTHEAST 192ND STREET RENTON, WASHINGTON ES-3215 INTRODUCTION General This geotechnical engineering study waa prepared for the proposed residential homes to be constructed on the vacant lot northwest of the intersection between Southeast 192nc1 Street and 1121h Avenue Southeast in Renton, Washington. The purpose of this study was to provide geotechnical recommendations for currently proposed development plans; Our scope of services for completing this geotechnical engineering study included the following: • Completing subsurface test pits for purposes of characterizing site soils; • Completing laboratory testing of soil samples collected at test pit locations; • Conducting engineering analyses, and; • Preparation of this report. The following documents and maps were reviewed as part of our report preparation: • Liquefaction Susceptibility Map 11-5 prepared by the King County Flood Control District, May 2010; • Surface Water Design Manual (KCSWDM) for King County, Washington, prepared by the Department of Natural Resources and Parks, January 9, 2009; • Amendments to the KCSWOM by the City of Renton, Washington, Public Works Department, February 2010; • Online Web Soil Survey (WSS) resource provided by the United States Department of Agriculture (USDA), Natural Resources Conservation Service, and; • Geologic Map of King County compiled by Booth et al., March 2007. Puget Sound Homes, LLC January 28, 2014 Revised February 4, 2014 Project Description ES-3215 Page2 We understand the subject tax parcel (King County Parcel No. 662340-0131) will be subdivided into two separate lots. Proposed development plans for each lot include a single-family residential home and associated driveway and utility improvements. We investigated the use of infiltration facilities, such as gravel filled trenches or drywells, for control of storrnwater flow resulting from new impervious surfaces. Preliminary development plans indicate impervious surface areas on the order of 4,000 square feet for each new lot. Our infiltration evaluation was completed with the understanding that the subject project will be submitted under the "Small Project Drainage Review" requirements identified in the referenced KCSWDM and the referenced City of Renton amendments to the KCSWDM. At the time of report submission, specific grading and building load plans were not available for review; however, based on our experience with similar developments, proposed residential structures will likely be on the order of two to three stories in height and constructed utilizing relatively lightly loaded wood framing supported on conventional foundations. We anticipate residential structures will incorporate slab-on-grade floors at the garage elevation. We anticipate perimeter footing loads on the order of 1 to 2 kips per lineal foot (kif). Slab-on-grade " .... Joadlng is anticipated to be on the order of 150 pounds per square foot (psf). If the above design assumptions are incorrect or change, ESNW should be contacted to review the recommendations in this report. ESNW should review final designs to confirm that our geotechnical recommendations have been incorporated into the plans. SITE CONDITIONS Surface The subject site is located northwest of the intersection between Southeast 192nd Street and 112th Avenue Southeast in Renton, Washington. The approximate location of the property is illustrated on Plate 1 (Vicinity Map). The square-shaped property consists of a single tax parcel which comprises approximately 0.50 acres. The site is bordered to the north and west by a single-family residential home, to the west by 112th Avenue Southeast, to the south by Southeast 192nd Street, and to the east by a drainage tract maintained by the City of Renton. The site is currently undeveloped and vegetation consists qf short lawn grass. Site topography is relatively level with little or no discemable elevation change. Subsurface An ESNW representative observed, logged, and sampled three test pits excavated at accessible locations within the property boundaries on January 20, 2014 using a mini-trackhoe and operator retained by our firm. The test pits were completed for purposes of assessing soil conditions and classifying site soils. Earth Solutions NW, LLC Puget Sound Homes, LLC January 28, 2014 Revised February 4, 2014 ES-3215 Page3 The approximate locations of the test pits are depicted on Plate 2 (Test Pit Location Plan). Please refer to the test pit logs provided in Appendix A for a more detailed description of subsurface conditions. Topsoil and Fill Topsoil was generally encountered in the upper four to six inches of existing grades. The topsoil was characterized by brown and dark brown color, the presence of fine organic material, and small. root intrusions. Fill was encountered between depths of approximately three to five-and-one-half feet below existing grades at the test pit locations. In general, fill consisted of loose silty sand with gravel and loose poorly graded gravel with sand (Unified Soil Classification System: SM and GP, respectively). Moisture content of the fill at the time of our fieldwork can generally be characterized as moist to wet. Native Soll Underlying topsoil and fill, native soils pr:imarily consisted .of medium dense silty sand (USCS: SM). Poorly graded sand with and without appreciable silt content (USCS: SP-SM and SP, respectively) was encountered at test pit locations TP-1 and TP-2 at depths of three and five- and-one-halffeet, respectively. Native soil was typically encountered in a moist to wet condition and extended to the maximum exploration depth of eight feet below existing grades. Geologic Setting The referenced geologic map resource identifies Vashon subglacial till deposits (Qvt) across the site and surrounding areas. As described on the geologic map resource, Vashon subglacial till deposits typically consist of compact diamicts of silt. sand, and subrounded to well-rounded gravel which were glacially transported and deposited under ice. In addition. the referenced WSS resource identifies Alderwood gravelly sandy loam (AgC) across the site and surrounding areas. The Alderwood series formed in moraines and glacial till plains. Based on our field observations, native soils on the subject site are primarily consistent with Vashon subglacial till deposits. Silty sand primarily encountered at depth during our subsurface ->Y.oloration was the orimarv basis for this interoretation. Groundwater During our subsurface exploration completed on January 20, 2014, groundwater seepage was encountered between depths of approximately three-and-one-half to seven feet below existing grades. Minor to moderate caving of the test pit walls was observed where grounctwater seepage was encountered. Iron oxide staining was generally encountered between rour-ar,.,.. one-half to six-and-one-half feet below existing grades. Earth SoitJtio~ : :· ... _ ?uget Sound Homes. LLC ,anuary 28. 2014 Revised February 4, 2014 ES-3215 Page4 In our opinion, groundwater seepage will be encountered during excavations for the proposed development site, including excavation activities for both foundation subgrades and utility installatlons. Groundwater seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, time of year, and soil conditions. in generai, groundwater flow rates are higher during the wetter, winter months. DISCUSSION AND RECOMMENDATIONS General In our opinion, construction of proposed residential homes is feasible from a geotechnical standpoint. The primary geotechnical considerations associated with the proposed development include foundation support, slab-on-grade subgrade support, the suitability of using on-site soils as structural fill, and drainage. In our opinion, proposed residential structures can be constructed on competent natiVe soil, recompacted native soil, or new structural fill. In _general, competent native deposits were encountered beneath topsoil and fill at depths of approximately three to six feet below existing grades. Where encountered, fill can likely be reworked to the specifications of structural fill, provided it Is at or near optimum moisture content at the time of placement and compaction and primarily free of organic and deleterious material. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with a suitable structural fill material, will be necessary. This study has been prepared for the exclusive use of Puget Sound Homes, LLC and their .• r1:1presentatives, No warranty, expressed or implied, is made. This study has been prepared in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. Site Preparation and Earthwork Site preparation activities will include installing temporary erosion control measures, establishing grading limits, and performing site stripping, as necessary. Temporary Erosion Control · We anticipate egress to the proposed residential lots will be provided from Southeast 192nd Street and a private access driveway. Prior to finished pavement installation, temporary construction entrances and drive lanes, consisting of 6 to 12 inches of quarry spalls, should be considered in order to minimize off-site soil tracking and to provide a stable access entrance surface. Geotextile fabric may also be considered underlying the quarry spalls for greater stability of the temporary construction entrance. Earth SoluUons WI, LLC Puget Sound Homes, LLC January 28, 2014 Revised February 4, 2014 ES-3215 Page 5 Erosion control measures should consist of silt fencing placed around down gradient margins of the site. Soil stockpiles should be covered or otherwise protected to reduce soil erosion. Temporary approaches for controlling surface water runoff should be established prior to beginning earthwork activities. Stripping Topsoil was generally encountered in the upper four to six inches of existing grades. ESNW should be retained to observe site stripping activities at the time of construction to better assess the degree of required stripping. Over-stripping may result in increased project development costs and should be avoided. Topsoil and organic-rich soil is neither suitable for foundation support nor for use as structural fill. Topsoil and organic-rich soil can be used in non-structural areas it desired. In-situ Soils . From a geotechnical s~ndpoint, native silty sand encountered at the test pit locations will generally not be suitable for use as structural fill, based on the conditions observed during our fieldwork completed on January 20, 2014. Native soils possess appreciable fines contents and maintain moisture sensitivity that is characterized as moderate to high. However, if remedial measures are incorporated into final designs and the overall constructioA schedule, riative soils may be suitable for use as structural fill. Remedial measures would likely include soil aeration, which would largely be achieved by performing grading activities during summer months of relatively low rainfall activity. Successful use of native soil as structural fill will largely be dictated by the moisture content at the time of placement and compaction. If site soils cannot be successfully compacted, the use of an imported soil may be necessary. In our opinion, a contingency should be provided in the project budget for export of soil that cannot be successfully compacted as structural fill if grading activities take place during periods of extended rainfall activity. Soils with fines contents greater than 5 percent typically degrade rapidly when exposed to periodis of rainfall. Imported Soils · Imported soil intended for use as structural fill should consist of a well-graded granular soil with a moisture content that is at or slightly above the optimum level. During wet weather conditions, imported soil intended for use as structural fill should consist of a well-graded ytanuiar soii with a fines content of 5 percent or less defined as the percent passing the Number 200 sieve, based on the minus three-quarter inch fraction. Subgrade Preparation Foundation and slab subgrade surfaces should be compacted in situ to a minimum depth of one foot below desian subarade elevations. Uniform compaction of the foundation and slab subgrade areas will establish a relatively consistent subgrade condition below the foundation and slab elements. ESNW should observe the compacted subgrade prior to placing formwork.. Earth Solution& rN>/. LI.C ~·.iget Sound Homes. LLC ~anuary 28, 2014 Revised February 4, 2014 Structural Fill ES-3215 Page6 Structural fill is defined as compacted soil placed in foundation, slab-on-grade, and roadway areas. Fills placed to construct permanent slopes and throughout retaining wall and utiiity trench backfill areas are also considered structural fill. Soils placed in structural areas should be placed in loose lifts of 12 inches or less and compacted to a relative compaction of 90 percent, based on the laboratory maximum dry density as determined by the Modified Proctor Method (ASTM 01557). Soil placed in the upper 12 inches of slab-on-grade, utility trench, and pavement areas should be compacted to a relative compaction of at least 95 percent. Additionally, more stringent compaction specifications may be required for utility trench backfill zones depending on the responsible utility district or jurisdiction. Foundations in our op,nron, proposea res,aentiai structures can be constructed on competent native soil, recompacted native soil, or new structural fill. In general, competent native deposits were encountered beneath topsoil and fill at depths of approximately three to six feet below existing grades. Where encountered, fill can likely be reworked to the specifications of structural fill. provided it is at or near optimum moisture content at the time of placement and compaction and primarily free of organic and deleterious material. Where loose or unsuitable soil conditions are- exposed at foundation subgrade elevations, compaction of the ·sons to the specifications of structural fill, or overexcavation and replacement with a suitable structural fill material, will be ,1ecessary. Provided foundations will be supported as described above, the following parameters can be used for design: • Allowable soil bearing capacity • Passive earth pressure • Coefficient of friction 2,500 psf 300 pcf (equivalent fluid) 0.35 A one-third increase in the allowable soil bearing capacity can assumed for short-term wind and seismic loading conditions. The above passive pressure and friction values include a factor-of- safety of 1.5. With structural loading as expected, total settlement in the range of one inch and differential settlement of approximately one-half inch is anticipated. The majority of the settlements should occur during construction, as dead loads are applied. Seismic Design The 2012 International Building Code (IBC) recognizes the American Society of Civil Engineers (ASCE) for seismic site class definitions. Based on the soil conditions observed at the test pit locations, in accordance with Table 20.3-1 of the ASCE Minimum Design Loads for Buildings and Other Structures manual, Site Class D should be used for design. Earth Solutions NW, LLC Puget Sound Homes, LLC January 28, 2014 Revised February 4, 2014 ES-3215 Page 7 The referenced liquefaction susceptibility map indicates the site and surrounding areas maintain very low liquefaction susceptibility. Liquefaction is a phenomenon where saturated or loose soils suddenly lose internal strength and behave as a fluid. This behavior is in response to increased pore water pressures resulting from an earthquake or other intense ground shaking. During our subsurface exploration completed on January 20, 2014, groundwater seepage was encountered between depths of approximately three-and-one-half to seven feet below existing grades. Minor to moderate caving of the test pit walls was observed where groundwater seepage was encountered. Iron oxide staining was generally encountered between four-and- one-half to six-and-one-half feet below existing grades. In our opinion, site susceptibility to liquefaction can be characterized as low. The generally consistent medium dense condition of the native soils at depth and the absence of a uniformly established groundwater table were the primary bases for this characterization. Slab-On-Grade Froora Slab-on-grade floors for proposed residential homet1 on the subiect site should be supported on a firm and unyielding subgrade. ·where feasible, native soil likely to be exposed -at slab-on- grade subgrade levels can be compacted in situ to the specifications of structural fill. Unstable or yielding areas of the subgrade should be recompacted qr oyerexcavated and replaced with suitable structural fill prior to construction of the slab. ' A capillary break consisting of a minimum of four inches of free-'.draining crushed rock or gravel ~hould be placed below the slab. Free-draining material should have a fines content of 5 percent or less (percent passing the Number 200 sieve, based on the minus three-quarter inch fraction). In areas where slab moisture is undesirable, installation of a vapor barrier below the slab should be considered. If a vapor barrier is utilized, it should be a material specifically designed for use as a vapor barrier and should be installed in accordance with the manufacturer's specifications. Retaining Walls Retaining walls must be designed to resist earth pressures and applicable surcharge loads. The following parameters can be used for design: • Active earth pressure (yielding condition) • At-rest earth pressure (restrained condition) • Traffic surcharge* (passenger vehicles) • Passive earth pressure -Coefficient of friction • Seismic surcharge • wnere app11cao1e •• Where H equals retained he1gm Earth Solutions IN/. U:: 35 pcf (equivalent fluid) 55 pcf 70 psf (rectangular distribution) 300 pcf (equivalent fluid) 0.40 6H** (active condition) 14H** ( at-rest condit'!c, . Puget Sound Homes, LLC January 28, 2014 Revised February 4, 2014 ES-3215 Page a The above design parameters are based on a level backfill condition and level grade at the wall toe. Revised design values will be necessary if sloping grades are to be used above or below retaining walls. Additional surcharge loading from adjacent foundations, sloped backfill, or other applicable loads should be included in the retaining wall design. Retaining walls should be backfilled with free-draining material that extends along the height of the wall and a distance of at least 18 inches behind the wall. The upper 12 inches of the wall backfill can consist of a less permeable soil if desired. A perforated drain pipe should be placed along the base of the wall and connected to an approved discharge location. A typical retaining wall drainage detail is provided on Plate 3. If drainage is not provided, hydrostatic pressures should be included in the wall design. Drainage In our opinion, perched groundwater will likely be encountered during excavations for the proposed development, including excavation activities for both foundation subgrades and utility installations. ESNW should be consulted during preliminary grading to identify areas of seepage and to provide supplement recommendations to reduce the potential for instability ... related to seepage effects. Temporary measures to control surface water runoff and . groundwater during construction would likely involve interceptor trenches and sumps . • . . Finish grades must be designed to direct surface drain water away from structures and slopes. Water must not be allowed to pond adjacent to structures or slopes. In our opinion, foundation drains should be installed along building perimeter footings. A typical foundation drain detail is provided on Plate 4. Limited lnflltratlon Design We investigated the feasibility of utilizing drywells and gravel filled trenches to accommodate stormwater runoff from new residential lots. The City of Renton adopts the referenced 2009 KCSWDM for design of infiltration facilities. The following recommendations can be utilized regarding proposed infiltration facilities on the subject site. Soil samples collected during our fieldwork were tested in accordance with the United States Department of Agriculture (USDA) textural analysis procedure. Native soils on the subject site primarily consisted of medium dense sandy loam in a moist to wet condition, with localized areas of fine sand and coarse sand. Infiltration characteristics typically exhibited by sandy loam, fine sand, and coarse sand can be characterized as low, n:ioderate, and high. Limited infiltration is allowed into sandy loam according to page C-49 of Appendix C in the referenced KCSWDM. Gravel filled trenches infiltrating into sandy loam should have a length of .125 feet for every 1,000 square feet of tributary impervious surface served. Orywells infiltrating into sandy loam should have a gravel volume of 380 cubic feet for every 1,000 square feet of tributary impervious surface served. Earth Solutions NW, LLC Puget Sound Homes. LLC January 28, 2014 Revised February 4, 2014 ES-3215 Page 9 Drvwells and gravel filled trenches should be designed in accordance with the referenced KCSWDM, which included typical design details for consideration. Provisions for overflow should be included in design of limited infiltration facilities. ESNW should be retained to provide additional geotechnical services in association with this project, including testing and consulting services during construction and installation of infiltration facilities. In addition, ESNW should have an opportunity to review final project plans prior to submittal. Excavations and Slopes The Federal Occupation Safety and Health Administration (OSHA) and the Washington Industrial Safety and Health Act (WISHA) provide soil classification in terms of temporary slope inclinations. Soils that exhibit high compressive strength are allowed steeper temporary slope inclinations than are soils that exhibit low compressive strength. Based on the soil conditions encountered at the test pit locations, soils likely to be exposed during excavation and grading activities would be classified as Type C by OSHA and WISHA. temporary slopes over four feet in height in Type C soils must be sloped no steeper than 1.5H:1V (Horizontal:Vertical). The presence of perched groundwater may cause caving of the temporary slopes. due to hydrostatic pressure. ESNW should observe site excavations to confirm soil types and allowable slope inclinations. If the recommended temporary slope inclinations cannot be achieved, temporary shoring may be necessary to support excavations. Permanent slopes should maintain a gradient.of 2H:1V or flatter and should be planted with vegetation to enhance stability and to minimize erosion. An ESNW representative should observe temporary and permanent slopes to confirm the slope Inclinations are suitable for the exposed soil conditions and to provide additional excavation and slope recommendations as _ necessary. Pavement Sections The performance of site pavements is largely related to the condition of the underlying subgrade. To ensure adequate pavement performance, the subgrade should be in a firm and unyielding condition when subjected to proofrolling with a loaded dump truck. Structural fill In pavement areas should be compacted to the specifications previously detailed in this report. It is possible that soft, wet, or otherwise unsuitable subgrade areas may still exist after base grading activities. Areas containing unsuitable or yielding subgrade conditions will require remedial measures such as overexcavation and thicker crushed rock or structural fill sections prior to pavement We anticipate new pavement sections will be primarily subjected to passenger vehicle traffic. For lightly loaded pavement areas subjected primarily to passenger vehicles, the following preliminary pavement sections can be considered: Earth Solutions t,NV, LLC Puget Sound Homes, LLC January 28, 2014 Revised February 4, 2014 ES-3215 Page 10 • Two inches of hot mix asphalt (HMA) placed over four inches of crushed rock base (CRB), or; • Two inches of HMA placed over three inches of asphalt treated base (ATB). The HMA. ATB and CRB materials should conform to WSDOT specifications. All soil base material should be compacted to a relative compaction of 95 percent, based on the laboratory maximum dry density as determined by ASTM 01557. Final pavement design recommendations can be provided once final traffic loading has been determined. City of Renton road standards may supersede the recommendations provided in this report. Utility Support and Trench Backfill In general, native soils primarily encountered at depth during our fieldwork will be suitable for support of utilities. Organic-rich soil is not considered suitable for direct support of utilities and may require removal at utility grades if encountered. Remedial measures may be necessary in some areas in order to provide support for utilities, such· as overexcavation and replacement with structural fill, or placement of geotextile. fabric. Groundwater seepage will likely be encountered in utility excavations and caving of trench walls may occur where groundwater is encountered. Dewatering, as well as temporary trench shoring, may be necessary during utility excavation and installation. From a geotechnical standpoint, native soils should be suitable for use as structural backfill in utility trench excavations, provided the soil is at or near optimum moisture content at the time of placement and compaction. Moisture conditioning of the soils may be necessary at some locations prior to use as structural fill, especially where groundwater seepage is encountered. Each section of utility lines must be adequately supported in the bedding material. Utility trench backfill should be placed and compacted to the specifications of structural fill as previously detailed in this report, or to the applicable specifications of the City of Renton or other responsible jurisdiction or agency. LIMITATIONS The recommendations and conclusions provided in this geotechnical engineering study are professional opinions consistent with the level of care and skill that is typical of other members in the profession currently practicing under similar conditions in this area. A warranty is not expressed or implied. Variations in tt)e soil and groundwater conditions observed at the test pit locations may exist, and may not become evident until construction. ESNW should reevaluate the conclusions in this geotechnical engineering study if variations are encountered. Additional Services ESNW should have an opportunity to review final project plans with respect to geotechnical recommendations provided in this report. ESNW should also be retained to provide testing and consultation services during construction. Earth Solutions NW, LlC ~1'11.b. .... .lt . ·-ff ><•••:,;_ ······-. -r- •• Reference: King County, Washington Map686 By The Thomas Guide Rand McNally 32nd Edition ., NOTE: This plate may contain areas of color. ESNW cannot be II responsible for aey sm,equent rrisinfel'Jnlation of lhe inlollnatlOO resulting ~om black & \\lllte reproductions of !his plate. ::I> .... .. \ .... J-~;: ' '· '-::·;t -J!Jt.l if ~:,'l'M_ •i, I ·, ',1;:F:;· .. a\ • Vicinity Map Dumas Heights -Lot 1 & 2 Renton, Washington .. !o_rw_n_. _G_Ls _ _.l._o_ate_o1_,2_812_01_4 ... 1Proj_·._No_. _32_1_s __ , 1 l .. c_h_eck_ed_K_o_H_...I o_a_te_Ja_n_. 2_0_1_4._j P_1a1_e ____ __,! !I I I I ' I J I I J I I J I I I I I J I I I I 1,------ l I I / ITP-3 I ' I I I 1 I I I / -•- ' " I 1 I / I I r t .. " I I I I l I I I !'bl 11;', I I I' l ~ ' I O: I' I i j --------------~ I : ! :--~~--- ~ t-· I> I I Q J•· I (31 ,------ 1 .g I I "' I TP-21 11 :!I I' I ! I UJ I I I ' l I I I -y- Ii I I I I I I l I I I I I ,I I f I I 1 : : : -TP-1 I ,1 I I I I ' ---·-:;_.·· __ -"- I I I I 1, I · I , I I I I -r---,- S.E. 192ND STREET LEGEND TP-1-jl-Approximate Location of ESNW Test Pit, Proj. No. ES-3215, Jan.2014 ___ 1 Subject Site D Proposed Building NOTE: The graphics shown on this plate are not Intended for design purposes or precise scale measurements. but only ti illus1rate the appn,xmale lest locations relative 1D the app!O)Cinale locations of e>isting and I or proposed site features. The inlbrmation ilus1ra1"d is largely based on dala provided by the client at the line of our study. ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. NOTE: This plalB may contain nee of color. ESNW carmot be responsible fir any subsequent misinleil>felation of the inlbrmation resulting from black & \\fJite reproductions of this plate. 1"=40' • Drwn. GLS Test Pit Location Plan Dumas Heights -Lots 1 & 2 Renton, Washington Date 01/2812014 Proj. No. 3215 Checked KOH Date Jan. 2014 Plate 2 II " NOTES: • Free Draining Backfill should consist of soil having less than 5 percent fines. Percent passing #4 should be ·25 to 75 percent. · • Sheet Drain may be feasible in lieu of Free Draining Backfill, per ESNW recommendations. '• l?':lin Pipe should consist of perforated; ngid PVC Pipe surrounded with 1" Drain Rock. LEGEND: Free Draining Structural Backfill 18" Min. Structural Fill Perforated Drain Pipe (Surround In Drain Rock) SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAWING RETAINING WALL DRAINAGE DETAIL Dumas Heights -Lots 1 & 2 Renton, Washington ... -----1---~;.;.;;.;....;:.;~_,l ·:I I Drwn. GLS I Date 01/2812014,Proj. No. 3215 • I Checked KOH I Date Jan. 2014 I Plate 3 ! ii " Slope ... ::· Perforated Rigid Drain Pipe (Surround with 1" Rock) NOTES: • • Do NOT tie roof downspouts to Footing Drain. • Surface Seal to consist of 12• of less permeable, suitable .soil. Slope away from building. LEGEND: Surface Seal; natiw soil or other low permeability material. 1 " Drain Rock SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAWING • FOOTING DRAIN DETAIL Dumas Heights -Lots 1 & 2 Renton, Washington Drwn. GLS Date 01/28/2014 Proj. No. 3215 Checked KOH Date Jan. 2014 Plate 4 Appendix A Subsurface Exploration Test Pit Logs ES-321:: The subsurface conditions at the site were explored on January 20, 2014 by excavating three test pits using a mini-trackhoe and operator retained by our firm. The approximate locations of subsurface exploration test pits are illustrated on Plate 2 of this studv. The subsurface test oit logs are provided in this Appendix. The test pits were advanced to a maximum depth of eight feet below existing grades. The final logs represent the interpretations of the field logs and the results of laboratory ma1vses. The stratification lines on the logs represent the approximate boundaries between ~on types. In actuality, the transitions may be more gradual. ·, Earth Solutions NW. ~- Earth Solutions NWuc SOIL CLASSIFICATION CHART MAJOR DIVISIONS SYMBOLS GRAPH LETTER TYPICAL DESCRIPTIONS COARSE GRAINED SOILS MOIU!THANSOll OFMAlEUALIS LARGER l1-fAH NO. 200 SIEVE SIZE FINE GRAINED SOILS MORE THAN 5°" OF MATERIAL IS SMALLER THAN NO. 200 SIEVE SIZE GRAVEL AND GRAVELLY SOILS MORE 1lWI 5°" OFCOIIRSE fRACT10N RETAINED ON NO. 4SIEVI! SANO ANO SANDY SOILS CLEAN GRAVELS GRAVELS WITH FINES (APPRECIABLE AMOUNT Of FJNES) CLEAN SANDS (LITTLE OR NO FINES) SANDS WITH MORETIWt5°" FINES OF COARSE FRACTION PASSING ON NO. 4 SIEVE (APPRECIABLE SILTS AND CLAYS SILTS AND CLAYS AMOUNT OF FINES} LIQUID LIMIT LESSTHAN50 UQUIOLIMIT GRfATER THAN t50 HIGHLY ORGANIC SOILS .: t!rt!J t.!t t!f t!, t!t ~II GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT WEU.-GRADED GRAIIELS, GRAVEL- SANO MIXT\JRES, LITTLE OR NO FINES POoRI. Y-GRADED GRAVELS, GRAVEL -SAND R*T\IRES, UTTLE OR.NO ANES SO.TY GRAVELS, GRAVEL-SAND - SLT~ CLAYEY GRAIIELS. GRAVEi.-SAND- CLAY MllmJRE8 WEI.UlRADED SANDS, GRAVELLY SANDS, UTn.E OR NO FINES POOR!. Y-GRADED SNIDS, GRAVELLY SAN>, UTlU! OR NO FINES SO.TY SANDS, SAND-SILT MXTIJRES CLAYEY SANOS. SAN>-CLAY MIXTURES INORGANIC SIL TS MID VERY FINE SANDS, ROCK FLOUR, Sil.TY OR CLAYEY FIN& SANDS OR ClAYEY SU...TS WITH SUGKT PLASTICITY INORGANIC ClAYS OF LOW TO MEDILU PLASTICITY, GRAVELLY CLAYS. SANDY CLAYS. SILTY CLAYS. L£AN CLAYS ORGAIIC SILTS MID ORGNIIC SILTY ClAYS OF LOW P\AST1CITY INORGANIC SLT'S, MICACEOU9 OR DJ.+.TOMACEOUS FINE SAND OR SILTY SOILS INORGANIC CLAYS OF HIGH PlASTICfTY ORCANIC ClAYS OF MEDIUM TO HIGH PlASTICfTY, ORGANIC SLTS PEAT, HUMUS, SWN/IP SOILS WITI! HIGH a!GANIC CONTENTS DUAL SYMBOLS are used to indicate bordertine sod classifications. The discussion in the text of this report is neceseary for a proper understanding of Iha nature of the material presented In Iha attached logs_ • Earth Solutlona NW 1805-136111 Place N.E., Suite 201 Bellevua, Washington 9800!i Telephone: 426--449-47114 TEST PIT NUMBER TP-1 I PAGE 1 OF 1 Fax: 425-449-4711 CUENT Puget Sound !:!C!!l!tl•.J, l,l.bbl,C'---··---------------·------ PROJECT NUMBER 3215 ... DAT!! STARTED 1/20/14 .... . COIIPLl!TED Jf20/14 ...... !XCAVATION CONTRACTOR NW Exan,allng .. !XCAVATION llll!THOD PROJECT NAME ~1"feill!lll .. ,J,~.1 &2 .... PROJECT LOCAllON -. Wahington GROUND ELEVATION 47311 GROUND WATER LEVELII: AT TIME Of EXCAVATION - TEST PIT SIZE LOOOl!D 8Y KDff CHECKED BY KOH ATENDOFEXCAVATION ------··--... .. .... --.. ···-· NOTES Deptll of TopooN & Sod 6": fiecd 9'NO! ... 1-- 5 TESTS MC=6.80'!1, Fines • 3. 1 O'!I, MC = 22.3()'!1, SP. SM I AFTEREXCAVATION - MATERIAL DESCRIPTION Dartc brown TOPSOIL, roo1a 1o 1' Brown poo,ty gtadad GRAVB.. with sand, loose, molal (Fill) [USDA Claulllcallon: -.ly coarse SAND) -5" dalk brown organics layer -·-·-···--~------·· Brown poor1y g,aded SANO with lift, medium denae, - -moderate~ -113.5' to 4.5' -model'8le caving Imm 3.5' to 5' ·· . j -. \Jj 8 o ... Gray .poorly graded SAND, medium cleMe, ---------- --MC = 22.20'!f, SP /\ ' I 8.0 -Iron oxide staining -~~-toBOH Test pit terminated at 8.0 -below exlatlng grada. Grnundwalllr seepage enc:ourihmld at 3.5 and 7.0-during excavatlo!I. Bottom of_ pH at a.o-. . _4701 ••so Earth SolUliOna NW 1 eo5 • 136111 Place N.E , Suile 201 Bell8We, Washington 98005 Telephone: 425"449-4704 TEST PIT NUMBER TP-2 PAGE 1 OF 1 Fax: 425-4<19-4711 CLIENT Pugel sound Homes, LLC PROJECT NUMBER 3215 PROJECT NAIR Dumas Heights • Lois 1 & 2 PROJl!CT LOCATION Renton, Washington DATE 8TARTEO 1/20/14 COIIPLETED 1/20/14 GROUND l!Ll'iVATION 474 ft TEST PIT SIZE EXCAVATION CONTIIACTOR NW Excavating GROUND WATER LEVl!LS: EXCAVATION METHOD LOGGED BY KOH CHECKED BY KOH AT TIME OF EXCAVATION ··• AT END OF EXCAVATION -- AFTER EXCAVATION -NOTl!S o.,pth ofTapeoil & Sod 4"· 6": neld grass TESTS MATERIAL DESCRIPTION 0 TPSL . . o.s Dari< brown TOPSOIL, roob1 to 1.5' - 5 MC : 17.50% MC = 25.50% Finn= 11.00% Brown silty SANO with gnavel, loose, moist (FiU) -tan silty sand interbads -becomes moist to wet -heavy groundwatet seepage to BOH, minor caving to BOH, becomes - Brown poorly graded SAND with silt. medium dense, wet -iron oxide sta1ni ng {USDA C!assdicalion: fine SANO) Test ptt terminated at 6.5 feet below existing grade. Groundwater seepage encountered at 5 O -during excavation. Bottom of teet pit at 6.5 feet 473.5 ..... 467 5 • Earth Solullons NW 1805 • 136111 Plate N.E .• Suile 201 Bellevue. Washington 9800S Telephone: 425-449--4704 TEST PIT NUMBER TP-3 I PAGE 1 OF . Fax: 425,,448,,4711 CLIENT Puget sound Hanes, LLC PROJECT NUIIIBER 3215 PROJECT-Dumaa Heighla • Lola 1 & 2 PROJl!CT LOCATION Renton. Washington DATI STARTED 1/20/14 COIIIIPLE11!D 1/20/14 GROUND ELEVATION 474 ft TEST PIT SIZE EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVl!LS: l!XCAVATION IIIE'TltOD LOGGED BY KOH CHECKED BY KDH AT 1lllE OF EXCAVATION -• ATENDOFEXCAVATION -- AFTER EXCAVATION -NOTES Oeptlt of Topaoil & Sod 4"-6": field grm 0 j TESTS MCm20.50% MC = 23 20% Fines • 28.90')6. MC•21.10% ' I I 7._D MATERIAL DESCRIPTION Brown TOPSOIL. roots to 0.5' Brown silly SAND with graWJI, -. moist (Fil) .t,ec;omes dalk brown, -to medium denoe e.-. silly SAND, medium -. moiSI -iron oxide staining, moderllle---flom4.5' toS.5', --- [USDA C~: fine sandy LOAM) -beCCNnea dense Test pit tann..-al 7.0 feet below exfsllng grade. Groundwater,_. enco~ at4.5-dunngaxcavauon Bollom of-p. at 7.0 feel. 473.5 470.0 4670 .opendix B Laboratorv Test ;:i .. ,.,.,c-- ES-32'if Earth Solutions NW, LLC .._ ·• J Earth Solutions NW '\ 1805 -136111 Place N.E., Suite 201 ', ·. Bellevue, WA 98005 • • -_.,-Te4ephone: 425-2M,3300 CLIENT . Pugj,t $Qund I k!!!.ii/4 .. PROJECT NUIIBEII: Es.3215 U S. SIEVE OPENING IN INOIES GRAIN SIZE DISTRIBUTION ·----__ PROJ_ECT_LOC_CA_TIO_ N .~~."'----'~ U.S. SIEVE NUMBERS HYDROMETER e -1-3 2 1.s-1 314 112319 3 4 a e 10 1418 20 30 40 so m 1oo"Mo20D · 100 95 90 85 80 75 70 ... 65 I llO > 55 ID "' w 50 3, . IL ... 45 ~ 40 w a. 35 30 25 20 15 10 5 0 100 10 1 0.1 0.01 0:001 "!'-I -------. EMAIL ONLY Report Distribution ES-3215 Puget Sound Homes, LLC P.O. Box 1945 Sumner, Washington 98390 Attention: Mr. Robert Elllott Earth Solutiona t>tN, LLC